1. Field of the Invention
The present invention relates to a device for checking numbers and a method for checking numbers, which can be applied in a digital television decoder, especially designed for comparing PID numbers (Packet Identifier) of received data packets.
2. Brief Description of the Background of the Invention Including Prior Art
The method of implementing a PID filter (Packet Identifier) was described in the patent application EP 0 949 808. According to this method a table is created. The table stores values used for the purpose of comparison. The system uses a comparator to find out whether the given values—the first from circuit inputs and the second from the table—are equal. Moreover, a FIFO type (First-in, First-out) output queue is also applied. The output FIFO queue allows for initiating read operations, until such a time that the input data packet is defined as the correct one. When the PID data are given onto the system inputs, the comparator compares the given value with the stored values table, which was created earlier by the programming circuit.
In the case of joining or multiplexing of two signal streams, in which certain services have the same PID numbers, packets from the two services may mix. This may, at a later stage of signal processing, cause a conflict of PID numbers.